The present invention relates to a pressure-sensitive magnetic transfer recording medium. More particularly, it relates to a pressure-sensitive magnetic transfer recording medium which allows an impact printer to easily produce printed images having high magnetic characteristics capable of being read by means of a magnetic ink character reader (hereinafter referred to as "MICR").
MICR is designed to read printed magnetic images, such as characters or marks, printed with an ink containing a magnetic substance powder on a bill, check, credit card, pass, traffic census card or the like, by means of a magnetic head. The magnetic head in the MICR converts magnetic variations in magnetic images comprising various characters or marks into predetermined signals, the voltages of which are detected to recognize the characters or marks.
Characters or marks to be read by means of the magnetic head are required to have predetermined shape, dimensions and allowable ranges of dimensions as well as a predetermined magnetic signal level. In Japan, the allowable ranges with respect to E13B type face adopted in American Bank Association are prescribed in JIS X 9002.
E13B type face prescribed in JIS X 9002 consists of 14 characters in all, including 10 numerals (0 to 9) and 4 special marks. With respect to each character for E13B type face, JIS X 9002 prescribes nominal height, width and corner radius, and allowable ranges of these nominal dimensions as well as the allowable range of void.
In addition to E13B type face, there is CMC-7 type face as type face for MICR. CMC-7 type face is designed to form a character by arranging 7 longitudinal bars with 2 kinds of intervals and any character of CMC-7 type face can be magnetically recognized by combinations of 2 kinds of intervals. CMC-7 type face consists of 41 characters in all, including 10 numerals, 26 large alphabets and 5 special marks. A standard with respect to dimensions and magnetic characteristics of CMC-7 type face characters is prescribed by ECMA (European Computer Manufacturers Association).
Printed images of the above-mentioned type faces for MICR are formed by using a pressure-sensitive magnetic transfer recording medium which is produced by applying a magnetic ink composition usually composed of a magnetic substance powder and a vehicle comprising a resin and an oil on a support such as plastic film and drying the resultant coating to form a pressure-sensitive transferable magnetic ink layer. Using an impact printer such as a typewriter and a wire dot printer, the pressure-sensitive transferable magnetic ink layer of the recording medium is selectively transferred onto a receiving paper by action of pressure to form a magnetic image.
With respect to impact printers for MICR, there is a trend wherein the striking pressure in printing is lowered from the viewpoints of low noises and low costs and, hence, there is an increasing demand for high transfer sensitivity in pressure-sensitive magnetic transfer recording media used in such impact printers.
It is possible to cope with the high transfer sensitivity by means such as use of a resin having a low glass transition point, an increase of the amount of the plasticizer component contained, or the like. However, these means cause drawbacks such as blocking of an ink ribbon and production of printed images with poor scratch resistance. Herein, the term "blocking" refers to the phenomenon wherein when an ink ribbon having an ink layer on a support wound in the form of a roll is exposed to a high temperature enviroment, the ink of the ink layer is migrated to the rear side of the support contacting the front side of the ink layer, and the ink layer and the support adhere to each other, resulting in hindrance in unwinding the ink ribbon.
In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a pressure-sensitive magnetic transfer recording medium which is capable of preventing blocking of the pressure-sensitive transferable magnetic ink layer during storage at high temperatures as well as the lowering of the scratch resistance of printed images which are caused by increasing the transfer sensitivity of the conventional magnetic ink layer.
This and other objects of the present invention will become apparent from the description hereinafter.